Britney Spears "can't stop smiling" on holiday.

The 'Womanizer' hitmaker is currently on vacation in Hawaii with boyfriend Jason Trawick, and the couple have made no attempts to hide their love for one another.

One onlooker said: "Britney and Jason seem completely in love and happy. Britney has not stopped smiling since she arrived in Maui, and she seems to have the best time with Jason.

"Even in the ocean, they kept smooching. ... Britney also looks fabulous in her different bikinis, and Jason is in great shape as well."

The blonde beauty is said to be staying in a luxury ocean front suite and has been enjoying a succession of spa treatments and gourmet meals.

While Britney and Jason enjoy their break, the 28-year-old singer's sons Sean Preston, four, and three-year-old Jayden James - her children with ex-husband Kevin Federline - have also been given the opportunity to play in the surf, with the blonde beauty's parents Jamie and LYNNE SPEARS taking them on a trip to Santa Barbara.

A source said: "Britney told Preston and Jayden that she was going to the beach and promised the boys that they would get to go also. The boys had the best time in Santa Barbara with their grandparents."

The two boys showed no sign of missing their mother as they played in the sand.

One onlooker told "Preston and Jayden had a blast on the beach. Jamie and Lynne seemed to very much enjoy spending time with the boys, and together they built sand castles and played tag.

"The boys looked so cute and were beyond excited about the beach. Jamie and Lynne looked very happy together as well."